Evaluation of Positional Accuracy of OpenStreetMap Data for Urban Navigation in Lagos Metropolis

Volunteered geographic information platforms such as OpenStreetMap have become widely used for urban navigation, logistics, and emergency response in rapidly growing African megacities. This study evaluates the positional accuracy and completeness of OpenStreetMap road data for selected districts within Lagos Metropolis, the most densely populated urban centre in West Africa. A reference dataset is compiled from official topographic maps and GPS field surveys covering a stratified sample of road segments across high-density, medium-density, and low-density land use zones. Positional displacement is computed for 300 road segment midpoints, and completeness ratios are calculated by comparing OSM feature counts against reference data counts. Statistical comparisons are performed using mean error, root mean square error, and Pearson correlation coefficients. Results indicate that OSM road data in central Lagos achieves mean positional errors below ten metres in well-mapped areas such as Victoria Island and Lagos Island, while accuracy degrades significantly in peripheral districts and informal settlements. Completeness is above eighty percent in commercial corridors but drops to below fifty percent in newly developed estates on the Lekki peninsula. The findings have direct implications for navigation applications, delivery logistics firms operating in Lagos, and humanitarian mapping initiatives. The study recommends targeted field mapping campaigns and data quality audits to improve OSM coverage in underrepresented areas. Keywords: OpenStreetMap, positional accuracy, volunteered geographic information, Lagos, road network.